Compatibility Range in Polymer Mixtures. An approach using analogue calorimetry and group contribution procedures

The mixing enthalpies of blends of polymethylmethacrylate (PMMA) with poly(styrene-co-acrylonitrile) (SAN) were investigated by analogue calorimetry through the determination of the excess enthalpies of pseudobinary model mixtures corresponding to the addition of methyl-i-butyrate to a binary mixture of acetonitrile or propionitrile plus toluene or ethylbenzene. A group contribution procedure, based on UNIQUAC equation, was also devised and the polymeric mixing enthalpies were calculated from properly defined group contributions. Enthalpies for polymeric interactions were introduced into the Flory-Huggins equation and the miscibility window of PMMA-SAN mixtures was calculated. The results show a qualitative agreement with the experimental miscibility data and indicate that both the analogue calorimetry and the group contribution procedures yield correct results when acetonitrile, and not propionitrile, is chosen as the model for the polyacrylonitrile repeat unit of the copolymer. This revised version was published online in July 2006 with corrections to the Cover Date.     

Swelling of metallic surfaces irradiated by helium ions

At doses close to threshold for exfoliation or bubble formation the surfaces have been investigated by SEM and, after isolation of surface layers, also by RBS. Swelling as a function of energy and material has been determined. The data are interpreted in the form of volume occupied by a helium atom. We find an indication for a volume decrease with increasing energy. A special example of blister formation is also discussed, where we find evidence for a non-uniform fracture plane.     

Excess thermodynamics properties of propyl propanoate+hexane+cyclohexane at 298.15 K

Summary In this paper we present excess molar volumes and excess molar enthalpies of binary and ternary mixtures containing propyl propanoate, hexane and cyclohexane as components at 298.15 K. Excess molar volumes were calculated from the density of the pure liquids and mixtures. The density was measured using an Anton Paar DMA 60/602 vibrating-tube densimeter. Excess molar enthalpies were obtained using a Calvet microcalorimeter     

Organic-coated silver nanoparticles in biological and environmental conditions: Fate,stability and toxicity

This review paper presents the overview of processes involved in transformation of organic-coated silver nanoparticles (AgNPs) in biological systems and in the aquatic environment. The coating on AgNPs greatly influences the fate, stability, and toxicity of AgNPs in aqueous solutions, biological systems, and the environment. Several organic-coated AgNP systems are discussed to understand their stability and toxicity in biological media and natural water. Examples are presented to demonstrate how a transformation of organic-coated AgNPs in an aqueous solution is affected by the type of coating, pH, kind of electrolyte (mono- or divalent), ionic strength, organic ligands (inorganic and organic), organic matter (fulvic and humic acids), redox conditions (oxic and anoxic), and light. Results of cytotoxicity, genotoxicity, and ecotoxicity of coated AgNPs to food chain members (plants, bacteria, and aquatic and terrestrial organisms) are reviewed. Key factors contributing to toxicity are the size, shape, surface coating, surface charge, and conditions of silver ion release. AgNPs may directly damage the cell membranes, disrupt ATP production and DNA replication, alternate gene expressions, release toxic Ag⁺ ion, and produce reactive oxygen species to oxidize biological components of the cell. A progress made on understanding the mechanism of organic-coated AgNP toxicity using different analytical techniques is presented.     

离子液体1-乙基-3-甲基咪唑醋酸盐的制备及用于纤维素溶解纺丝的研究进展

离子液体1-乙基-3-甲基咪唑醋酸盐（[EMIM3Ac）可以溶解天然高分子等许多聚合物,尤其对于纤维素具有较强的溶解能力,且溶解过程基本不造成纤维素降解,故可以作为纤维素的有效溶剂,用于纤维素的溶解加工。与其它溶剂相比,[EMIM]Ac具有使用安全、不污染环境、易回收循环利用等优势,故在纤维素溶解、纺丝方面具有广阔的应...     

Prediction of vapor-liquid equilibrium from excess enthalpy data for binary ether +n-alkane or cyclohexane mixtures

Vapor liquid equilibrium (VLE) is successfully predicted from excess enthalpy H^E data for binary ether + n-alkane or cyclohexane mixtures. Parameters for the continuous linear association model (CLAM) and for the UNIQUAC Model for the excess Gibbs energy G^E were determined from H^E data measured at a low temperature (ambient temperature). These parameters are used to predict VLE data at low and high temperatures. The dependence of the accuracy of predictions on the set of H^E data chosen to evaluate the parameters and on the model for G^E are discussed.     

Enthalpies of solution and crystallization of ammonium aluminum sulphate dodecahydrate in water at 25°C

Enthalpies of crystallization of NH₄Al(SO₄)₂·12H₂O from aqueous solutions at 25°C, measured using a calorimetric method and determined from previously published data on the concentration dependence of the enthalpy of solution, are reported. The results are compared with the values obtained from the temperature dependence of solubility and from vapor pressure data by using the Williamson equation. The integral and partial molar enthalpies of solution in concentrated and diluted solutions are given.     

Molecular recognition: A thermodynamic study of non bonded interactions in aqueous solutions of iminoacids. Effects of steric and geometric isomerism

Enthalpies of dilution of binary and ternary aqueous solutions containing L-and D-proline, cis-L- and cis-D-4-hydroxy proline, trans-L-4-hydroxy proline, have been determined by flow calorimetry at 25°C. Pairwise self-and cross-interaction coefficients of the virial expansion of the excess enthalpies were evaluated. They are positive for solutions of unsubstituted prolines. On the contrary, upon the introduction of a hydroxy group, they become negative, reaching the largest value for the cis-L-lcis-D-4-hydroxy proline system. The results are interpreted in terms of preferential configurations, stabilized by interactions between the hydrophilic groups.     

阿莫西林分散片溶出度光纤化学传感在线过程检测

采用双波长法消除赋形剂的干扰,利用六通道光纤化学传感原位过程分析仪(FOCSDT)在线监测阿莫西林分散片溶出度。FOCSDT的平均校准曲线方程为y=188.38x+0.7607,回归系数r为0.9998。阿莫西林分散片的溶出数据与中国药典(Ch.P)方法对照无显著性差异。FOCSDT法无需取液、稀释等手工操作,能实时监测药物溶出全过程,为速释制剂内在质量的检测提供良好的手段。